In the manufacture of furniture such as tables, case goods, cabinetry, desks, shelves and related items, a wide variety of materials have been used. For instance, depending upon the desired market and price, furniture materials may range from low cost plastic molded units and particle board constructions to mid range wooden laminates to higher end premium wood or metal construction. Where a real wood or a high quality simulated wood appearance is sought, such products are difficult to find in a durable, versatile furniture. Furniture constructed from particle board is extremely heavy, has poor strength characteristics, and suffers from a loss of integrity when exposed to moisture. Laminated wood products are easily damaged and are difficult to repair since the surface features and texture of the laminate covering are not shared with the underlying wood or particle board substrate.
Accordingly, there is a need for improvements for providing finished furniture, case good products, and laminated panels which overcomes the limitations of the prior art.
It has now been discovered that a process and resulting product provides for a furniture grade, non-wood laminate which is useful in a variety of furniture constructions. The laminate comprises a thermoformable sheet which may be molded into a desired configuration. An interior cavity formed by curved edge walls formed in the thermoformable sheet is then used as part of a mold cavity into which a polyurethane foam is injected and cured. Following curing of the foam, the exposed foam surface may be covered with a decorative paper, vinyl, or fabric covering.
Typically, the resulting laminate is interconnected to other laminate pieces or, in the example of a laminated table top, legs may be attached to the laminated top. Accordingly, appropriate mounting or attachment hardware may be suspended or placed within the cavity by appropriate jig(s). The jigs hold the mounting hardware in the desired three-dimensional spacial orientation during the foaming and curing step.
Upon hardening of the structural foam, the mounting hardware is permanently attached to the laminate by the adhesive properties of the cured foam. The cured structural foam also imparts a great deal of rigidity to the resulting laminate, yet adds little additional weight. The thermoplastic molded sheet and the interior molded foam of the laminate are largely impervious to water, durable, and may be further milled, sawed, drilled or worked as needed for use as a laminate in general furniture making needs.
The resulting laminates may be made of a wide range of thicknesses to accommodate various construction needs. The thermoformable materials may be selected from extruded sheets of pigmented and wood grained poly-vinyl chloride (PVC). PVC materials have an accepted appearance within the market place and may be provided in a number of color combinations. Further, various types of texture may be molded into the PVC sheet when thermoformed. Combined with the nearly indestructible properties of PVC along with the ease of repair of scratches and other blemishes, PVC has useful attributes as a laminate component. When used as part of a rigid foam laminate, a PVC sheet having a thickness of 2-3 mm provides a laminate having excellent strength and rigidity properties. However, other thermoformable sheet material may be used in place of the PVC.
The use of a thermoplastic material, such as PVC, has advantages in that the surface of the laminate may be easily repaired by using various grades of sandpaper or steel wool and buffing with a rubbing compound to restore the surface of the damaged laminate to an attractive state. Conventional furniture laminates of pressed wood fibers or thin surface veneers are difficult to repair in a manner which restores an original appearance.
The ability to position and mold in situ the attachment hardware simplifies assembly of a finished furniture article. Further, the assembled article is stronger than similar articles made from a compressed wood or whole wood since the material integrity is not compromised by conventional hardware installation techniques. Since no cutting, drilling, or other invasive action is applied to the substrate, the material integrity is maintained. This improvement is important given that failure or weakening of attachment sites and hardware is a common occurrence in traditionally constructed furniture.
Hence, in one aspect, the invention resides in a method for making a laminate panel useful in furniture making. The laminate is formed by a process in which a sheet of a high impact wood grained PVC of about 2 mm in thickness is heated in an oven to a softening temperature. The heated PVC sheet is then stamped between a male and female mold into a form which, in one sample embodiment, may resemble a tray which defines a cavity area. The tray cavity is positioned within a foam molding station with the tray cavity being accessible to one or more jigs. The jigs are used to suspend inserts, such as mounting hardware and/or structural reinforcements, into the tray cavity area. The tray area is filled with a structural foam such as polyurethane using standard foam reagents and methods. Conventional polyurethane foam reagents and methods are well known within the art as set forth in U.S. Pat. Nos. 5,972,260 and 5,941,622 which are incorporated herein by reference.
The foam cures into a rigid structure which surrounds the insert portions positioned within the cavity. The tray is then inverted so that the tray top may form the upward-facing surface of a table top, counter top, or similar article. Legs or other attachments may then be made using the inserts or mounting hardware previously foamed in place.
In another aspect, the invention resides in the foregoing method and resulting product wherein the inserts are suspended partially within the cavity but do not make contact with the PVC molded article. The sequential foaming and curing steps thereby provides a layered structural foam between the sheet material and the insert. In accordance with this invention it has been found that by avoiding direct contact between a load bearing insert and the thermoformable sheet, a better distribution of forces occurs. As such, bulges or indentations which may otherwise occur from the transfer of forces between an insert and the laminate surface material are avoided.
In yet another aspect of this invention, it has been found that the strength of conventional inserts used in the present laminated construction may be improved by increasing the surface area and/or orientation of the insert with respect to the foam substrate. For instance, the strength between the foam and a bracket may be increased by providing an angled bend to the bracket portion within the foam. The structural integrity of the foam laminate portion may be increased by altering the three-dimensional shape of the laminate as well. Further, the incorporation of structural members having a higher rigidity than the thermoplastic laminate may be used. Such structural members may be of wood, steel, or rigid plastic. These inserts may be placed in high stress areas and may be installed in a manner similar to various attachment hardware.
These and other aspects of the invention will be described in greater detail in reference to the drawings.